Back: Measure length of pet’s back from the
base of the neck to the base of the tail. See below for
estimating by breed.Neck: Measure the circumference of pet’s neck
for a snug fit. No need to add inches as you would with a
collar.Chest/Girth: Measure girth around the
broadest part of the chest and add 2”.

Review: I ordered the XS in this after measuring my 7.2lb (14 inch chest) Pom..... unfortunately there is NO way it will fit her! I plan on returning this item for a larger size. Strange how this brand is so off with there sizing!